Get-Office365Information.ps1

<#
    .SYNOPSIS
    Performs operations in a restartable fashion against Office365.

    .DESCRIPTION
    This script takes care of ensuring that connections to Office365 are valid
    before processing mailboxes, will automatically reconnect to Office365 when
    the session is broken, and allows an administrator to "recover" to either a
    specific two-letter username prefix or continue from a specific mailbox when
    the process dies.
#>
[CmdletBinding()]
param (
    [Parameter(Mandatory=$false)]
    [ValidatePattern("[a-zA-Z]{2}")]
    [string]
    # The first two letters of the username to start with. The default is "aa".
    $StartingPrefix = "aa",
    
    [Parameter(Mandatory=$false)]
    [string]
    # The full username of the mailbox to start with. Processing will continue from there.
    $StartingMailbox = "",
    
    [Parameter(Mandatory=$true)]
    [System.Management.Automation.PSCredential]
    # The Office365 credentials to use.
    $Credential,
    
    [Parameter(Mandatory=$false)]
    [System.Management.Automation.Runspaces.PSSession]
    # An already-existing connection to Office365 that should be used.
    # Probably not tested enough to really use.
    $Session = $null
)

<#
    .SYNOPSIS
    Creates a new Office365 session.
#>
function New-Office365Session {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory=$true)]
        [System.Management.Automation.PSCredential]
        # The credentials to use to connect to Office365.
        $Credential
    )
    
    Write-Verbose "Destroying any previous sessions"
    Get-PSSession | ? { $_.ComputerName -match 'outlook.com' -and $_.ConfigurationName -eq 'Microsoft.Exchange' } | Remove-PSSession
    
    $msoExchangeURL = “https://outlook.office365.com/powershell-liveid”
    Write-Verbose "Creating new session to $msoExchangeURL"
    $oldPref = $VerbosePreference
    $VerbosePreference = "SilentlyContinue"
    $session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri $msoExchangeURL -ErrorAction Stop `
                             -Credential $Credential -Authentication Basic -AllowRedirection -Verbose:$false
    Write-Verbose "Importing session"
    $null = Import-PSSession $session -Prefix Office365 -AllowClobber -Verbose:$false
    $VerbosePreference = $oldPref
    return $session
}



$a = [int][char]'a'
$z = [int][char]'z'

if (![String]::IsNullOrEmpty($StartingMailbox)) {
    $StartingPrefix = $StartingMailbox.Substring(0,2)
}

$totalPrefixes = [Math]::Pow(($z-$a+1), 2)
$processedPrefixes = 0
$processedMailboxes = 0

foreach ($1 in $a..$z) {
    foreach ($2 in $a..$z) {
        $prefix = ("{0}{1}" -f [char]$1, [char]$2)
        
        $complete = [Int32]($processedPrefixes/$totalPrefixes * 100)
        Write-Progress -Id 1 -Activity "Processing mailboxes" -Status "Progress ($processedPrefixes of $totalPrefixes):" `
                       -CurrentOperation "Prefix '$prefix'" -PercentComplete $complete
        
        if ($prefix -lt $StartingPrefix) {
            #Write-Verbose "Skipping $prefix (comes before requested starting prefix of $StartingPrefix)"
            $processedPrefixes++
            continue
        }
        
        if ($Session -eq $null -or $Session.State -ne "Opened") {
            $Session = New-Office365Session -Credential $Credential
        }

        Write-Verbose "Getting all mailboxes for prefix '$prefix'"
        $mboxes = Get-Office365Mailbox -ResultSize Unlimited $prefix* -ErrorAction SilentlyContinue | Sort-Object Name
        
        $processedMailboxes = 0
        foreach ($mbox in $mboxes) {
            if ($mbox -eq $null) { continue }

            $pctComplete = [Int32]($processedMailboxes/$mboxes.Count * 100)            
            Write-Progress -Id 2 -ParentId 1 -Activity "Processing mailboxes starting with $prefix" `
                           -Status "Progress ($processedMailboxes of $($mboxes.Count)):" -CurrentOperation $mbox.Name -PercentComplete $pctComplete

            if (![String]::IsNullOrEmpty($StartingMailbox) -and $mbox.Name -lt $StartingMailbox) {
                Write-Verbose "Skipping $($mbox.Name) (comes before requested starting mailbox $StartingMailbox)"
                $processedMailboxes++
                continue
            }
            $StartingMailbox = ""

            if ($Session -eq $null -or $Session.State -ne "Opened") {
                $Session = New-Office365Session -Credential $Credential
            }

            ###############################################
            ###                                         ###
            ### Do not alter the code above this point! ###
            ###                                         ###
            ###############################################


            # DO YOUR PROCESSING RIGHT HERE.
            # Call another function or put your code directly
            # between the comment blocks.


            ###############################################
            ###                                         ###
            ### Do not alter the code below this point! ###
            ###                                         ###
            ###############################################
        }
        Write-Progress -Id 2 -ParentId 1 -Activity "Processing mailboxes starting with $prefix" -Status "Progress:" -Completed
        $processedPrefixes++

    }
}
Write-Progress -Id 1 -Activity "Processing mailboxes" -Status "Progress:" -Completed